1. Field of the Invention
The present invention is directed to a printer capable of a high speed printing of a large number of characters on a medium and, more particularly, to an automatic printer having a plurality of replaceable character printing members for printing a large quantity of characters, such as the symbols of the Japanese or Chinese language.
2. Description of the Prior Art
As can be appreciated by those versed in the Japanese written language, three forms of writing are frequently utilized. These include a normal written form of a Japanese-like alphabet with approximately 52 characters known as, Hiragana. Supplementing the Hirakana form of printing is another written character system called Katakana which is basically a phonetic forming of words in writing. Finally, a relatively complex and numerous character writing form with a large number of characters is utilized called Kanji. The derivation of the Kanji characters is from China and requires a knowledge of symbols running into the thousands. Each symbol can convey a word or phrase to the reader. Approximately a minimum of 2,000 Kanji characters are required as a vocabulary of written characters for a printer. The Kanji form of writing is preferred in Japan since it has a capability of conveying more complex thoughts and meanings than that of the other writing styles of Katakana and Hiragana. Frequently, a written document will integrate all three styles of writing simply because certain words, such as Western derived words, may have to be formed in Katakana because there is no equivalent Kanji symbol in the Japanese language. As can be appreciated, the net effect of this relatively sophisticated and complex form of writing is to create relatively complex problems in providing an automatic printer.
Japanese character typewriters are known and generally utilize a bed of type font that is individually selected in a panographic manner with a selecting stylus from a table of characters. Chinese, or Kanji, printers must utilize a large number of characters, e.g., approximately 2,000, as compared to the alphabetic, or English, character printer. The large number of characters required has necessitated a relatively complicated and expensive mechanism. There have been suggestions to use an impact style printer which employs individual characters on a character drum. However, problems exist with the use of a character drum relating to the complicated control mechanisms required for a drum containing such a large number of characters. In addition, it is difficult to obtain high printing speed with sufficiently high quality print. To date, there are no known serial Chinese character printers suitable for the commercial market with satisfactory print quality and printing speed. At the present time, a Japanese syllabus is utilized for the printing of Japanese language sentences.
A prior art example of a serial character teleprinter having a plurality of type font units retreivable from a storage receptacle is disclosed in U.S. Pat. No. 3,892,303. Manual and electrical controls are provided wherein the font units can be changed automatically in response to a coded signal defining the desired font unit. An automatic tabular position memory is provided to record the carriage position at the time of initiation of a font unit change so that after the font unit removal and change, the carriage can automatically be returned to the original position along the writing line and printing is resumed. The controller is capable of selectively replacing a font unit to imprint a desired character as the printing line is continually advanced.
A dot-matrix printer utilizing electromagnetic members for driving print wires is suggested in U.S. Pat. No. 3,904,011. Generally, in a dot-matrix method of printing 24.times. 24 dots are required to simply obtain a medium quality print. The problem of manufacturing the required number of wire-dots with an appropriate pitch increases the resultant cost of the printer. In addition, the required character memory for an automatic printer is relatively expensive, since 576 bits per character are required.
Electrostatic printers are also known and provide an adequate density of dots for the formation of the character. However, there is still the disadvantage of requiring a large character memory and also, it is not possible to produce a carbon copy during the printing. An ink-mist printer and optical printer have also been suggested in the prior art to attain high printing speed. These, however, have the same disadvantage of requiring a large character memory and of not being able to produce a carbon copy. A supersonic beam printer is suggested in U.S. Pat. No. 3,907,089 and is cited simply of general interest.
U.S. Pat. No. 3,907,091 is cited simply to disclose a print wheel for a serial printer. U.S. Pat. Nos. 3,913,722; 3,904,015; and 3,890,894 are cited of general interest to disclose additional printed mechanism.
In summary, high quality print has been attained in the prior art with a serial printer which employs a character ball, or character wheel. However, the quantity of characters that can be automatically printed out with an advantageous printing speed is extremely limited. Suggestions have been made to utilize more than one printing head, however, problems occur in the period of time necessary to exchange the print heads. This problem is further compounded when a large number of characters are required, for example, in a Kanji Japanese printer. To date, there are no known serial Kanji printers having a suitable cost for a commercial market with satisfactory printing quality and printing speed. When it is required to print Japanese characters, generally, Hiragana or Katakana must be resorted to and Kanji will only be utilized where necessary with a resulting increase in cost and reduction in speed.